Science Buddies: "Ask an Expert"

Hi,

My project is to build a soil mouisture sensor and circuit.
I need help about using what kind of metal probes and
to design the circuit. My goal is to build an inexpensive
sensor and its circuit.

Thank you much in advance.

Hi Tunç,
That's an interesting project. There are many types of soil moisture probes. Do you know which type you would like to design? One of the simplest and cheapest designs is an electrical conductivity probes than can be built with nails, wire, and resistance meter. Gypsum block sensors are only slightly more complicated and are more reliable. More info on these particular devices is available here:
http://www.sowacs.com/archives/98-02/msg00000.html

I look forward to hearing more about your project.

Chris